The effects of elevated carbon dioxide concentration on leaf growth and development in Populus

The composition of the Earth’s atmosphere is changing. Such changes can largely beattributed either directly or indirectly to anthropogenic activities. However, the effectsthat these changes will have on terrestrial vegetation in the future, represents an areaof great uncertainty. The results that have been published in the literature havegenerally concluded that elevated atmospheric carbon dioxide concentration ([eCO2])causes increased above- and below-ground biomass compared to ambient conditions.Members of the Populus genus have risen to the forefront of plant research into theeffects of [eCO2]. Members of the genus are extremely fast-growing, making themsuitable candidates for use as biomass energy crops. The Populus trichocarpasequence was released in 2006, hence unveiling a huge genetic resource to the plantscience community.Although a large amount of studies to date have been dedicated to the effects of[eCO2] on plant growth, few have focussed on the underlying genetic basis of thechanges. However, thanks to the genetic resources that are now freely available, thishas now been addressed. In the series of experiments presented in this thesis acombination of morphological measurements, gene expression and protein studieswere used to assess the effects of [eCO2] on Populus leaves.The results of the studies presented here have shown that there were somedifferences in various aspects of plant growth as a result of [eCO2], although themagnitude of the response was lower than has been reported previously in theliterature. However, there were rather few changes in transcript expression (asassessed by microarrays) due to [eCO2]. This conclusion was reproducible acrossdifferent microarray platforms. This result was further confirmed by a proteomicsexperiment, which showed that there were no proteins whose abundance differedsignificantly between ambient and elevated [CO2].It is possible that [eCO2] causes an additive effect on gene expression and hence thesensitivity of the techniques was such that these differences could not be identified.However, it may be possible that the plants demonstrate a plastic response to [eCO2]and that the techniques used to assess the response were inappropriate in this case. Insuch an instance, more targeted studies on particular biosynthetic pathways of interest(such as cell wall biosynthesis) may be more appropriate for any future trials